Typically, gas turbine engines include a compressor for compressing air, a combustor for mixing the compressed air with fuel and igniting the mixture, and a turbine blade assembly for producing power. Combustors often operate at high temperatures that may exceed 2,500 degrees Fahrenheit. Typical turbine combustor configurations expose turbine vane and blade assemblies and turbine rotors to these high temperatures. As a result, turbine rotors must be made of materials capable of withstanding such high temperatures. Steel rotors have begun to be changed to nickel-based alloys to compensate for these high temperatures. However, rotors are large components and forming the rotors entirely of nickel-based alloys is expensive. Thus, a need exists for a more cost efficient turbine rotor having superior thermal properties.
Modern steam turbines currently operate without cooling at temperatures close to, or even exceeding 600° C. These are almost exclusively manufactured from ferritic steels. However, the maximum temperature at which these steam turbines can operate is close to that at which the steam turbine operates. The ferritic steels capable of being used at highest operating temperatures have poorer low temperature capabilities, thus it is desirable to be able to produce rotors which allow the rotor mechanical behavior to be optimal at all temperatures.